1. Field of the Invention
The present invention relates to a reinforced matrix for a molten carbonate fuel cell and a method for preparing the same.
2. Description of the Prior Art
A molten carbonate fuel cell (MCFC) comprises a cathode in which carbonate ions are generated from the reaction of oxygen, carbon dioxide and electrons, an electrolyte which enables the carbonate ions to easily move, a matrix and an anode in which hydrogen is oxidized to generate electrons and reacts with the carbonate ions to form water.
The matrix supports a fluent liquid phase electrolyte at high temperature, thereby fixing it therein. In order to support the liquid electrolyte in a good manner, the matrix is needed to have a fine porous structure.
A size of the pore and a porosity typically required for the matrix is 0.1˜0.5 μm and 40˜70%, respectively <Handbook of Fuel Cells. Volume 4 (2003), pp. 357-356>. Ceramic materials of α, β or γ-type LiAlO2 (lithium aluminate) etc. are used for the matrix.
In order to form a suitable fine structure, a particle size of the ceramic material is required to be 1 μm or less and a surface area thereof is required to be 10 m2/g.
However, when the matrix for MCFC consists of the fine particles having such large surface area, the strength thereof becomes considerably lowered, so that the matrix is easily collapsed.
In order to solve the problem, macro particles having an average size of 50 μm or alumina fibers have been added to reinforce the matrix in the art.
In the art, however, the strength is not sufficiently increased even in case of adding the macro particles. Further, the alumina fiber is expensive and becomes unstable at environments where the MCFC operates <C. Y Yuh, C. M. Huang and M. Fraoogue, Advanced in carbonate fuel cell matrix and electrolyte. Proceedings of the Fourth International Symposium on Carbonate Fuel Cell Technology, Electrochemical Society Pennington, N.J. (1997), pp. 6678>.
Meanwhile, recently, aluminum has been added to the conventional matrix to make a reinforced matrix <C. M. Huang and C. Y Yuh, U.S. Pat. No. 5,869,203, Feb. 9, 1999>.
According to the method, the aluminum reacts with the electrolyte to form LiAlO2, which results in a loss of the electrolyte. In addition, it is very difficult to control the fine structure of the matrix for MCFC according to the method. Furthermore, since the strength is increased after the aluminum reacts with the electrolyte, there is a drawback that the matrix is easily broken before the aluminum reacts with the electrolyte.
A matrix that consists of titanium carbide, zirconium carbide, aluminum oxide, Li2CO3 and the like and reacts with the oxygen during the operation to form Li2TiO3, LiAlO2 and Li2ZrO3 is known <U.S. Patent Publication No. 2004/0062981>. However, the strength of the matrix is not increased.